Constant voltage circuits such as linear regulators are provided in power supply devices used for electronic apparatuses. To stably operate without oscillation, a capacitor is added to an output of a constant voltage circuit in some cases. However, to achieve sufficient current driving abilities, the output capacitor has to be very large and the mounting area of the output capacitor has to be large. Accordingly, output capacitance requirements for this purpose may hinder efforts in miniaturization and cost reductions of constant voltage circuits. On the other hand, when an output capacitor is minimized or omitted altogether, stability of the constant voltage circuit suffers and oscillation easily occurs.
This problem is addressed by connecting amplifiers to phase compensation capacitors in constant voltage circuits, thereby forcing large phase compensation capacitances. In such a case, stability of a constant voltage circuit is improved, but high speed performance of the constant voltage circuit suffers. Thus, this technique may limit the frequency characteristics of the circuit. Furthermore high speed operation in a constant voltage circuit may result in increased current consumption.